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Fri, 17 Jun 2022 04:19:14 -0700 (PDT) Date: Fri, 17 Jun 2022 19:19:10 +0800 From: Muchun Song To: David Hildenbrand Cc: Oscar Salvador , corbet@lwn.net, akpm@linux-foundation.org, paulmck@kernel.org, mike.kravetz@oracle.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, duanxiongchun@bytedance.com, smuchun@gmail.com Subject: Re: [PATCH v2 2/2] mm: memory_hotplug: introduce SECTION_CANNOT_OPTIMIZE_VMEMMAP Message-ID: References: <20220520025538.21144-1-songmuchun@bytedance.com> <20220520025538.21144-3-songmuchun@bytedance.com> <53024884-0182-df5f-9ca2-00652c64ce36@redhat.com> <24d5ec20-9c9e-93aa-11f4-c4619f51f7d1@redhat.com> <186924ab-651f-71a1-93d2-3500a67dffee@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1655464757; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; 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dmarc=pass (policy=none) header.from=bytedance.com; spf=pass (imf07.hostedemail.com: domain of songmuchun@bytedance.com designates 209.85.216.47 as permitted sender) smtp.mailfrom=songmuchun@bytedance.com X-Rspamd-Server: rspam01 X-Rspam-User: X-HE-Tag: 1655464756-995648 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, Jun 17, 2022 at 06:49:15PM +0800, Muchun Song wrote: > On Fri, Jun 17, 2022 at 12:14:02PM +0200, David Hildenbrand wrote: > > On 17.06.22 11:54, Oscar Salvador wrote: > > > On Fri, Jun 17, 2022 at 09:43:33AM +0200, David Hildenbrand wrote: > > >> VmemmapSelfHosted, then the function names get nicer. > > > > > > Definitely. > > > > > >> > > >>> +#endif > > >>> + > > >>> /* > > >>> * On an anonymous page mapped into a user virtual memory area, > > >>> * page->mapping points to its anon_vma, not to a struct address_space; > > >>> diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c > > >>> index 1089ea8a9c98..e2de7ed27e9e 100644 > > >>> --- a/mm/hugetlb_vmemmap.c > > >>> +++ b/mm/hugetlb_vmemmap.c > > >>> @@ -101,6 +101,14 @@ void hugetlb_vmemmap_free(struct hstate *h, struct page *head) > > >>> { > > >>> unsigned long vmemmap_addr = (unsigned long)head; > > >>> unsigned long vmemmap_end, vmemmap_reuse, vmemmap_pages; > > >>> + struct mem_section *ms = __pfn_to_section(page_to_pfn(head)); > > >>> + struct page *memmap; > > >>> + > > >>> + memmap = sparse_decode_mem_map(ms->section_mem_map, > > >>> + pfn_to_section_nr(page_to_pfn(head))); > > >> > > >> Why can't we check the head page directly? Either I need more coffee or > > >> this can be simplified. > > > > > > Uhm, maybe I'm the one who needs coffe here but we have something like: > > > > > > [ hot-plugges section ] > > > [memmap pages][normal pages] > > > > Oh, right, we need the memmap for our hugetlb page (which resides in the > > reserved section), but these are not marked. We need the memmap of that > > memmap. > > > > I assume one could directly via the page address. Because we want the > > memmap of the memmap. > > > > vmmemmap_page = virt_to_page(head); > > > > I think this can works, more simple. > Oh, I forgot virt_to_page() cannot applicable for vmemmap addresses. I think Oscar's approach is right. > Thanks. > > > Not sure, though, if that would work with that function. >